Strain-specific mouse tumors grow non-specifically when wrapped in muscle grafts syngeneic to the intended allogeneic host. The non-specific growth of the allogeneic tumor-syngeneic muscle sandwich (TMS) is not serially transferable, and does not appear to sensitize the recipients to H-2 antigens syngeneic to the TMS-tumor. Spleen cells of TMS-bearers are not responsive to TMS-tumor H-2 antigens on adoptive transfer of immunity. The TMS-graft evokes a foreign body reaction out of which clones of viable tumor cells develop. The object of the proposal is to establish mechanisms by which the non-specific growth of the antigenic TMS-tumor escapes immunological destruction. Studies are designed to evaluate: 1) alteration of antigenicity and immunogenicity of the TMS-tumor during latency period, 2) effect of foreign body reaction cells on success of TMS-tumor growth, 3) the TMS-host afferent (sensitizing) and efferent (cytotoxic) limbs of the immune response, and 4) T-cell lesions that may be associated with the success of the TMS-tumor. Particular emphasis will be placed on the cellular kinetics of the immune reactive cells during non-specific growth of the strain specific tumor. Growth of the TMS-tumor appears to be analogous to those conditions which occur spontaneously during tumor development in an autochthonous host. The dynamic interaction of the tumor-host balance will be emphasized as a means of explaining how antigenic tumors escape immunologic destruction.